can understudy
Regular verb: understudy - understudied- understudied

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can understudy
you can understudy
he can understudy
we can understudy
you can understudy
they can understudy 	I can be understudying
you can be understudying
he can be understudying
we can be understudying
you can be understudying
they can be understudying	I can have understudied
you can have understudied
he can have understudied
we can have understudied
you can have understudied
they can have understudied	I can have been understudying
you can have been understudying
he can have been understudying
we can have been understudying
you can have been understudying
they can have been understudying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot understudy
you cannot understudy
he cannot understudy
we cannot understudy
you cannot understudy
they cannot understudy 	I cannot be understudying
you cannot be understudying
he cannot be understudying
we cannot be understudying
you cannot be understudying
they cannot be understudying	I cannot have understudied
you cannot have understudied
he cannot have understudied
we cannot have understudied
you cannot have understudied
they cannot have understudied	I cannot have been understudying
you cannot have been understudying
he cannot have been understudying
we cannot have been understudying
you cannot have been understudying
they cannot have been understudying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I understudy?
can you understudy?
can he understudy?
can we understudy?
can you understudy?
can they understudy? 	can I be understudying?
can you be understudying?
can he be understudying?
can we be understudying?
can you be understudying?
can they be understudying? 	can I have understudied?
can you have understudied?
can he have understudied?
can we have understudied?
can you have understudied?
can they have understudied? 	can I have been understudying?
can you have been understudying?
can he have been understudying?
can we have been understudying?
can you have been understudying?
can they have been understudying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I not understudy?
can you not understudy?
can he not understudy?
can we not understudy?
can you not understudy?
can they not understudy? 	can I not be understudying?
can you not be understudying?
can he not be understudying?
can we not be understudying?
can you not be understudying?
can they not be understudying? 	can I not have understudied?
can you not have understudied?
can he not have understudied?
can we not have understudied?
can you not have understudied?
can they not have understudied? 	can I not have been understudying?
can you not have been understudying?
can he not have been understudying?
can we not have been understudying?
can you not have been understudying?
can they not have been understudying?